The invention relates in general to metallurgical furnaces and in particular to a new and useful device for changing tap runners on shaft furnaces.
The tapping of pig iron and slag from a blast furnace occurs at periodical intervals. Depending on the quantity of pig iron produced, there are eight to twelve taps in 24 hours. In the tapping process, the pig iron and slag are separated in a "main tap runner". In recent times such main tap runners on large blast furnaces are given large cross sections. The main tap runner is followed as a rule by additional tap runners and tilting runners for pig iron (to the site of transfer to ladles or "torpedo cars") and slag. While the slag is being discharged from the main tap runner, the pig iron remains in this runner between taps.
With pig iron tap quantities of several thousands of tons daily, the refractory lining of the main tap runner is subject to considerable mechanical and thermal load and consequently to high wear. For this reason it is necessary to repair or completely renew the lining of the runner at regular intervals. The durability of tap runners before the next repair is for example, about 50,000 tons of pig iron; complete renewal occurs after a production of about 120,000 to 130,000 tons of pig iron.
In the case of blast furnaces with more than one tap hole, work on the runner is carried out on the spot in the casting house. During this repair period, the pig iron is tapped from another tap hole, and usually also in a second casting house, so that as a rule this results in either no restrictions, or only minor restrictions of the operation.
The situation is entirely different, however, with blast furnaces which have only one tap hole. Such blast furnaces must be run throttled for the duration of the repair or renewal of the refractory runner lining or, if the work takes more time, the blast furnaces must be shut down.
This fact has suggested the idea to change the main tap runner with the aid of the casting house crane. Or, in the case of main tap runners composed of several sections, the procedure was to change individual sections in need of renewal in the described manner.
Because of the previously mentioned large dimension of the main tap runner, a considerable crane capacity is needed for runner replacement, and, of course, the casting house steel structure must be correspondingly strong. Besides, large areas are needed in the casting house where the removed runner sections can be stored for repair and relining.
Known also is a device for changing the main tap runner of a blast furnace (German patent application No. P 36 24 266.7) in which there are arranged before the tap hole of the blast furnace, on the mill floor, at least four hoisting elements in a stationary or non-stationary manner. These elements engage at cross-heads on which the main tap runner rests. It is possible to lower the runner to be replaced onto transport means located on the mill floor, in particular a track-bound one, and to raise the newly lined runner from the transport means to the level of the casting platform. The main tap runner with the cross-heads is held by means of pneumatically actuated holding arms arranged at the steel structure of the casting platform.
Although with this known device quick changing of the tap runner becomes possible, its installation requires preparatory work, such as earthwork for the retractable hoisting elements.